Method IntersectBox

Common/DataModel/vtkBox.cxx:308–423

------------------------------------------------------------------------------ Bounding box intersection modified from Graphics Gems Vol I. The method returns a non-zero value if the bounding box is hit. Origin[3] starts the ray, dir[3] is the vector components of the ray in the x-y-z directions, coord[3] is the location of hit, and t is the parametric coordinate along line. (Notes: the intersecti

// coordinate along line. (Notes: the intersection ray dir[3] is NOT
// normalized.  Valid intersections will only occur between 0<=t<=1.)
char vtkBox::IntersectBox(const double bounds[6], const double origin[3], const double dir[3],
  double coord[3], double& t, double tolerance)
{
  bool inside = true;
  char quadrant[3];
  int i, whichPlane = 0;
  double maxT[3], candidatePlane[3];

  // Make sure tolerance is non-zero
  double tol = (tolerance <= 0 ? FLT_EPSILON : tolerance);

  // Make sure bounds are not degenerate (i.e., have positive volume); pad by
  // tolerance if it is.
  double bds[6];
  for (i = 0; i < 3; ++i)
  {
    if ((bounds[2 * i + 1] - bounds[2 * i]) > 0)
    {
      bds[2 * i] = bounds[2 * i];
      bds[2 * i + 1] = bounds[2 * i + 1];
    }
    else
    {
      bds[2 * i] = bounds[2 * i] - tol;
      bds[2 * i + 1] = bounds[2 * i + 1] + tol;
    }
  }

  //  First find closest planes
  //
  for (i = 0; i < 3; i++)
  {
    if (origin[i] < bds[2 * i])
    {
      quadrant[i] = VTK_LEFT;
      candidatePlane[i] = bds[2 * i];
      inside = false;
    }
    else if (origin[i] > bds[2 * i + 1])
    {
      quadrant[i] = VTK_RIGHT;
      candidatePlane[i] = bds[2 * i + 1];
      inside = false;
    }
    else
    {
      quadrant[i] = VTK_MIDDLE;
    }
  }

  //  Check whether origin of ray is inside bbox
  //
  if (inside)
  {
    coord[0] = origin[0];
    coord[1] = origin[1];
    coord[2] = origin[2];
    t = 0;